Character-oriented protocols (also known as byte-oriented protocols) group information or control codes into full bytes (8 bits). One exemplary character-oriented protocol is the American Standard Code for Information Interchange (ASCII) character encoding. An ASCII character set defines characters in terms of byte information. For example, the byte “0100 0001” represents the character “A”. Various communication systems use character-oriented protocols. One exemplary system which uses a character-oriented protocol is the Aircraft Communications Addressing and Reporting System (ACARS) used in aircraft air-to-ground communications. In ACARS, a set of ASCII characters can be transmitted over the system as defined in the Aeronautical Radio, Incorporated (ARINC) 618-6 Air/Ground Character-Oriented Protocol Specification.
In contrast to character-oriented protocols, bit-oriented protocols use a stream of individual bits to transfer information or control codes without grouping the bits into bytes. Bit-oriented protocols are typically less overhead-intensive than character-oriented protocols. Due to the lower overhead and/or other factors, many systems use bit-oriented protocols. For example, many line replaceable units (LRUs) used in an aircraft system communicate with one another using a bit-oriented protocol. In order for binary data from a bit-oriented protocol to be transferred over a character-oriented protocol, such as ACARS, a protocol conversion is needed. Conventional techniques for converting from a bit-oriented to a character-oriented protocol double the size of transmission data. In particular, the techniques described in the ARINC 622-4 ATS Data Link Applications over ACARS Air-Ground Network specification convert every 4 bits of the bit-oriented data to an 8 bit (1 byte) character. Although enabling the transmission of bit-oriented data over a character-oriented protocol, the increase in file size also increases the transmission time and the cost associated with ACARS transmissions since airlines typically pay for transmission of data over ACARS according to the number of bits sent.